In other words, he publicly harassed a colleague who (for what could be any number of perfectly valid reasons) preferred not to publicly state their beliefs. That would seem to me to be an eminently reasonable reason to fire someone. If you go around publicly harassing your colleagues to publicly state their political opinions, you deserve to be fired.
The fired employee Tweeted today:
>In the interest of transparency, I was let go for calling out an employee’s inaction here on Twitter. I stand by what I said. They didn’t give me the chance to quit [0]
He then specifically cited [1] the Tweet in question that was the cause:
>I asked @Vjeux to follow @reactjs's lead and add a statement of support to Recoil's docs and he privately refused, claiming open source shouldn't be political.
>Intentionally not making a statement is already political. Consider that next time you think of Recoil. [2]
This is specifically targeting an individual front-end engineer at FB, which in my own estimation crosses the line from criticism of executives or general policy, to specifically trying to instigate public outrage against a co-worker. If such actions were directed at me, I would definitely consider it as contributing to a hostile work environment. It all strikes me as a modern-day example of "Havel's greengrocer" [3].
[0] https://twitter.com/aweary/status/1271522288752455680
[1] https://twitter.com/aweary/status/1271531477209976832
[2] https://twitter.com/aweary/status/1267895488205869057
[3] https://en.wikipedia.org/wiki/The_Power_of_the_Powerless#Hav...
e.g. government employees initially raise concerns on policy privately, then resign and speak out when the discussions fail.